Correlations between the first principal component (PC1) and the physical properties of the sample. From left to right: correlation with the AGN luminosity at 5100 Å (L_5100 Å, in units of erg s⁻¹), the black hole mass (M_BH, in units of M_⊙), the Eddington ratio, the ratio R_FeII, and the viewing angle (i). Our three sources (Mrk 1044, SDSS J080101.41+184840.7, and, IRAS 04416+1215) are marked in green, while the other sources are marked in red. The Spearman’s rank correlation coefficients (ρ) and the p-values are reported for the correlations whenever the p-value < 0.001. The ordinary least-square fit for each panel is shown using a red solid line. The black dotted lines mark the confidence intervals at 95% for the 1000 realizations (dark gray lines) of the bootstrap analysis. The corresponding prediction intervals are shown in the background using a light gray color.